Fluid conduit assemblies, such as pipelines and hydraulic circuits, are used to transport an assortment of fluids, such as water, oil, various natural and synthetic gases, sewage, slurry, hazardous materials, and the like. Similar structures are utilized for transmitting electrical and fiber optic cabling across vast expanses of land in establishing telecommunication networks. The most commonly used conventional methods for repairing damaged fluid system components, such as carrier pipes, include the replacement of the component or the welding of a repair sleeve over the damaged section of the component. Such conventional remediation methods generally requires a costly interruption in system operation until the repair is completed. Furthermore, repairs based on such conventional remediation methods generally requires the costly and difficult transportation and handling of heavy repair parts, such as steel replacement components or steel repair sleeves for the remediation of damage in a metal pipe.
It has been established over the last two decades that composite repair system using a composite laminate can often provide a reliable and cost-effective means for repairing a damaged fluid system component. The installation of a composite laminate can often be performed without needing to interrupt operation of a fluid system. Furthermore, the materials that need to be transported and handled in order to install a composite repair system are lighter and less cumbersome than conventional repair materials, reducing the cost of making a repair as compared with replacing a damaged metal component or installing a metal repair sleeve.
In general, there are four types of composite repair systems. In one type of composite repair system, precured plies of a composite material (such as a glass fabric or a carbon fabric in a cured thermoset polymer matrix) are “glued together” ply-by-ply by using an adhesive as they are wrapped around a fluid system component that is being repaired. A commercial example of this approach is provided by the Clock Spring™ Repair Composite Sleeve manufactured by Clock Spring Company, L.P., of Houston, Tex. Some disadvantages of this approach include the fact that precured plies are generally quite rigid so that repairs can be difficult (and sometimes impossible) to perform on fluid system components, especially those possessing complex shapes.
In another type of composite repair system, a dry fabric (such as a dry glass fabric or a dry carbon fabric) is wrapped around the fluid system component that is being repaired. The fabric is then impregnated with an uncured resin, and the resin is cured. A commercial example of this approach is provided by the Carbon-Ply Composite Repair System manufactured by Crosslink Composites LLC of Wellsboro, Pa. One primary disadvantage of this approach is that the wetting of a wrapped (and hence multilayer) dry fabric in the field can incur the risk of poor final cured composite quality as a result of a possible undetected failure of an uncured resin formulation, especially if it does not possess an extremely low viscosity necessary to completely “soak through” the multiple layers of the dry fabric as required for proper impregnation. Installations made by using this approach are, hence, especially susceptible to quality variations related to field technician performance.
In another type of composite repair system, an uncured resin formulation is applied to a layer of a dry fabric before wrapping this layer of fabric (now in a wetted form) around a fluid system component. There are some inherent risks related to field technician performance during the impregnation of the fabric since the technician must start with a layer of dry fabric and impregnate it in the field before wrapping it around the fluid system component. This approach is used in many composite repair systems comprising two-part (resin and hardener) epoxy resin formulations. Many such formulations cure thermally at moderate temperatures once the two parts are mixed. Consequently, the two parts must remain unmixed until the product is ready to be installed in order to prevent premature curing. A commercial example is provided by the RES-Q™ Composite Wrap manufactured by T. D. Williamson, Inc of Tulsa, Okla.
In another type of composite repair system, a fabric (such as a glass fabric or a carbon fabric) is pre-impregnated in a manufacturing facility with an uncured resin. The resulting “wet” fabric (pre-impregnated with uncured resin) is packaged and transported to a repair site in a manner that protects it from premature curing. The wet fabric is subsequently removed from its packaging, wrapped around the fluid system component that is being repaired, and the resin is cured. When using a resin formulation that can be protected reliably from premature curing, this approach is preferable because it eliminates many quality risks associated with impregnating the fabric with an uncured resin in the field by performing the impregnation under controllable conditions in a factory. Two commercial examples are provided by Syntho-Glass™ XT and Viper-Skin™, manufactured by Neptune Research, Inc. of Lake Park, Fla., both of which use a moisture-curable polyurethane resin formulation. A bidirectional glass fabric is used in Syntho-Glass™ XT, while a hybrid bidirectional fabric woven by using a carbon fiber in one direction and a glass fiber in the other direction is used in Viper-Skin™.
Existing composite laminate materials targeted for use in repairing fluid system components are currently limited by the availability of only thermal curing, moisture-activated curing, and moisture-activated curing with thermal postcuring methods for obtaining a load-bearing composite laminate. These composite materials, however, are impractical in certain applications. For instance, proper installation of a moisture-cured or thermally-cured composite repair system may not be feasible in sub-zero environments, such as repairing sections of the Trans-Alaska Pipeline during the winter months. In another non-limiting example, the mileage of installed deepwater pipelines continues to grow rapidly. It is very cumbersome, as well as expensive, to perform deepwater pipeline repairs based on conventional repair approaches, some of which include installing clamps and/or connectors, replacing damaged pipe sections, and, if necessary, lifting a damaged pipe section to the surface rather than repairing it in the deepwater environment. Some related background information is provided by B. Povlovski, in “Deepwater Pipeline Repair—Lessons Learned and New Advances”, Proceedings of the 20th Deep Offshore Technology [DOT] International Conference, Houston, Tex., Feb. 12-14, 2008, which is hereby incorporated by reference herein in its entirety.
Composite laminates have not yet made many inroads into deepwater pipeline repairs, mainly because of aspects related to how the composite laminates are cured. Many thermally-curing composite laminates require threshold curing temperatures to obtain an acceptable level of cure at an acceptable rate. These threshold temperatures are oftentimes costly and difficult or otherwise impossible to achieve in deepwater environments and/or subzero temperatures. On the other hand, the use of a moisture-activated curing composite laminate in a deepwater environment is often hampered by its inherent tendency to cure prematurely upon exposure to the water in which a deepwater pipeline is submerged. The opportunity to expand the range of applications of composite laminates to include deepwater and cold pipeline repairs is just some of the many possible examples of why there is ongoing development of new methodologies for the repair of fluid system components by using composite laminate compositions that do not rely on thermal or moisture-activated curing as their primary curing mechanism.